Sean Doolittledidn't pitch in the pros until the instructional league last fall, but in two months, he's gone from Class A Stockton to Double-A Midland and, on Tuesday, to Triple-A Sacramento.

"He's at warp speed," A's director of player development Keith Lieppman said - and that was before Doolittle struck out four in 1 2/3 innings in his River Cats' debut later in the evening.

Once a top prospect as a first baseman, Doolittle - a pitcher and first baseman at the University of Virginia - decided to give relief pitching a try last summer after injuries sidelined him for a third year in a row. He didn't have a pickoff move; his secondary pitches weren't developed. At 25, he was looking at maybe a full year at Class A as he gained experience on the mound.

Doolittle defied projections, though, and he has rocketed back to be one of Oakland's best prospects again. The left-hander had a combined 0.84 ERA at Stockton and Midland, and he recorded 40 strikeouts in 21 1/3 innings. His fastball is in the mid-90s.

Doolittle is an excellent bet to be a September call-up, and he could be in the big leagues even sooner if he continues to gallop along as he has so far.

Defensive doings: The A's have been using the shift far more often this season than in previous years, and manager Bob Melvinbelieves the team is benefiting from it. When a hitter beats the shift it looks bad, but Melvin said it's working more often than not.

"It will never be 100 percent, but we feel like we have gotten a lot of outs with the shift," he said. "If we can make the whole field two-thirds of the field ... we're going to do it."

Briefly: Brandon McCarthywill throw a bullpen session Wednesday, and he is scheduled to come off the disabled list Saturday to start at Kansas City. ... Stockton left-hander Jake Brownwas named the California League Pitcher of the Week. In 38 innings, Brown has allowed 28 hits and four walks, and he has struck out 32.

A'S ON DECK

Wednesday

At Twins

10:10 a.m. No TV

Ross (2-5) vs. Liriano (0-5)

Thursday

Off

Friday

at Royals

5:10 p.m. CSNCA

Colon (4-5) vs. Paulino (2-1)

A'S LEADING OFF

Providing a spark: Outfielder Collin Cowgill might not be the odd man out, as had been expected, when Yoenis Céspedes returns Friday; he's reached base nine of his past 13 plate appearances, and the A's need baserunners.